Abstract

Platinum complex was introduced in low ratios (0, 1, 1.5, and 5 mol) as the third monomer in the conjugated backbone of well-known donor polymer PTB7-Th using a random terpolymer molecular design approach. All polymers showed similar absorption behavior and comparable HOMO/LUMO energy levels due to the small amount of Pt complex used. When blended with PC71BM in polymer solar cells, the power conversion efficiency was enhanced to 8.45 (obtained by the device based on PTB7-ThPt1.5 containing 1.5 mol Pt) compared with 7.92 for the control PTB7-Th. Notably, the apparently low molecular weight of PTB7-ThPt1.5 (Mn/Mw: 46/70 kg mol-1) compared with that of PTB7-Th (Mn/Mw: 62/97 kg mol-1) ensured a more convincing comparison. Using a combination of physical measurements, such as optoelectrical characterization, grazing incident wide-angle X-ray diffraction (GIWAXS), and picosecond time-resolved photoluminescence, the efficiency enhancement was contributed by the higher hole mobility, less bimolecular recombination, and a more efficient slow charge separation process.